Chlorination of hydrocarbons



Patented Apr. 10, 1951 UNITED STATES PATENT OFFICE 2,548,764 CHLORINATION F H'YDROC'ARBONS George W. Ayers Chicago, Ill., and Erskine E.

Harton, Jr., Alexandria, Va., assignors to The Pure Oil Company, Chicago, 111., a corporation of Ohio No Drawing, Application September 24, 1945, Serial No. 618,423

This invention relates to a method of chlorinating saturated hydrocarbons containing a tertiary carbon atom and more particularly to a method for separating saturated hydrocarbons which do not contain a tertiary carbon atom from other hydrocarbons. This application is a continuation-in-part of application Serial No. 474,748, now Patent No. 2,418,814, issued April 15, 1947.

An object of the invention is to selectively chlorinate saturated hydrocarbons containing a tertiary carbon atom in a mixture containing saturated hydrocarbons which do not contain a tertiary carbon atom.

Another object of our invention is to obtain saturated hydrocarbons not containing tertiary carbon atoms from an admixture containing saturated hydrocarbons of substantially the same boiling point containing tertiary carbon atoms.

Still another object of the invention is to provide a method for chlorinating hydrocarbons containing a tertiary carbon atom at or about atmospheric temperature. A still further object of the invention is to provide catalysts which accelerate the rate of chlorination of saturated hydrocarbons containing tertiary carbon atoms.

Other objects of the invention will become apparent from the following description. 7

We have found that certain metalwnitrates and nitrites not only greatly accelerate the rate or chlorination of saturated hydrocarbons containing tertiary carbon atoms, but that within an effective temperature range of approximately 70 to 150 F. the rate of chlorination of saturated hydrocarbons containing tertiary carbon atoms is greatly accelerated without materially accelerating the rate of chlorination of saturated hydrocarbons not containing at ter- 10 Claims. (01.260-659) tiary carbon atom, The metal nitrates and nitrites which are efiective as catalysts are those which are capable of reacting slowly with chlorine under reaction conditions to form nitrosyl ch ri c- .t lo nitrat aadri r ls rhish .we

have found to be particularly effective are uranyl, mercurous, mercuric, zirconium, thorium, cerium, zinc, copperjcadmium and calcium nitrates and nitrites. Thallium and cobalt nitrates and nitrities also exhibit a high degree of selectivity, but their ability to accelerate the chlorination of hydrocarbons containing a tertiary carbon atom is not as pronounced as the previously mentioned nitrates and nitrite's.

In accordance with our invention a mixture of hydrocarbons containing open chain parafiins and/or cycloparaifins not containing a tertiary carbon atom, such as normal 'hepta'ne and cyclohexane, and also containing .i'sopar'affins and/0r alkylated cycloparaffins containing a tertiary carbon atom such as iso-octane and-meth l 9 l xa e is pref ab y di solved in a s lvent w ch. i sub antially inert to the chlorinatins a en Al h u h the use of a solven is'nq necessary, it is preferred. ,Where a solvent not used very h mo rati s of droca bon to chlorinating agent mustfbe used to obtain good selectivity of chlorination. The ratio of hydrocarbon plus solvent to 91, lorinating agent should be at least 8 to 1 in order to get good selectivityrof chlorination andalso to avoid ex: plosivemixtures. s vents maybe used'nitrobenzene and organic chlorine containing compounds such as chloroform, carbon tetra chloridfi acetylene tetrachloride, hexachlorethane, and others. For best'results the volume of solvent used should be at least equal in volume to the hydrocarbon mixture. The volume of solvent to hydrocarbon may be maintained as-high as 10 to 1;or more.

As chlorinating agents for usein carrying out our process any mild chlorinating agent may be used, such as antimony pentachloride; sule furyl chloride, or even chlorinegas when used in such manner that its concentration inthe reaction mixture is sumci'ently' low. 'I he ch lori ti nt ma b fa'dfd d to h h o a o mixture toibechlorinated either continuously or c wise, c e being ta en, t m i i iriol ra o o hy roca bon. plu sol nt to hlor n i'n'g agent'm the mixtureabove a to 1; r i g r;

Although the temperature at which chlorination is effected may range from approximately 70 to 150 R, we prefer to maintain the temperature at approximately 70 to 90 F., since the selective action of the chlorinating agent is most pronounced within this temperature range.

Although it is not necessary to have the mixture absolutely dry during the chlorination reaction, we prefer to maintain the mixture dry for the reason that the chlorination reaction proceeds more rapidly in most cases in a dry environment than when moisture is present. As drying agents phosphorus pentoxide, sodium sulfate, and others, may be used. A very small quantity of drying agent is sufficient, as for example 0.5;pound, or less, per 100 pounds of solution to be chlorinated. Care should be exercised not to use alumina as drying agent in the presence of a chlorinating agent, since aluminum chloride forms and aluminum chloride is a nonselective chlorinating catalyst.

The time required for chlorination of substan- In order to demonstrate the effect of various metal nitrates in catalyzing the chlorination of saturated hydrocarbons containing a tertiary carbon atom, and saturated hydrocarbons not containing a tertiary carbon atom, a number of tests were made on normal heptane and isooctane. The tests were all carried out at temperatures of 70 to 80 F. and the chlorinating agent used was antimony entachloride. A mixture of the hydrocarbon to be tested in the amount of 10 mols to one mol of catalyst, 6 mols of phosphorus pentoxide, 50 mols of antimony pentachloride and 1180 mols of chloroform was used in each test, except those tests marked with an asterisk in which the ratio of reaction was 2 mols of hydrocarbon, one mol of catalyst, 6 mols of phosphorus pentoxide, 48 mols of' antimony pentachloride and 600 mols of chloroform. The

" mixtures were allowed to stand for 18 hours and tially all the isoparaffins, o r' other saturated hydrocarbons containing a tertiary carbon atom" will vary from approximately 4 to 20 hours, at a mperature of 70 to 90 F. when using dilute solutions of the hydrocarbons and high mol ratios of hydrocarbon to chlorinating agent. Longer periods of contact result in partial chlorinati n of the non-tertiary carbon atom hydrocarbons. Increasing the temperature decreases the time q red for chlorination, but also results in less selectivechlorination. Likewise, the higher the ratio of the chlorinating agent to hydrocarbon lfis t, the less the selectivity. The mixtu e 1 be Chlorinated may be preliminarily treated to e ove romatic and unsaturated hydrocarbons. This may be done either by treatment with 100% sulfuric acid at room, temperature; or b t h m n w th 100% sulfuric acid at temperatures of 32 to 40 F. followed by three successive treatmeme with 95 to 98% of sulfuric acid at approximately. the same temperature using one t tW0 :partsof acid to one part of hydrocarbon mixture;- or the aromatic, olefin and other unsaturated hydrocarbons may be removed by'a preliminary chlorination step at approximately normal atmospheric temperature in the absence of the catalyst. These hydrocarbons are readily chlorinated before chlorination of the saturated hydrocarbons takes place. In the event that it is not required to obtain substantially pure chlorinated hydrocarbons it is not necessary to remove the aromatic and other unsaturated hydrocarbons as a preliminary step, since these hydrocarbons will be chlorinated together with the isoparaffins and alkylated cycloparafiins.

IWhere the process is carried out for the purpose of separating iso-hydrocarbons, that is saturated hydrocarbons containing a tertiary carbon atom, from other saturated hydrocarbons, the mixture treated should be a narrow-boiling fraction. preferably a fraction having a boiling range not exceeding 50 to 75 F., in order that the nonchlorinated hydrocarbons may be separated from the chlorinated hydrocarbons bydistillation.

The process shouldwbe carried out in apparatus constructed of materials which are immune to attack by chlorine. Steel, aluminum and carbon surfaces should be avoided since ferric chloride, aluminum chloride, charcoal, and other forms of carbon are non-selective chlorination catalysts. Apparatus lined with glass or ceramic material is suitable.

then analyzed to determine the amount of chlorine that reacted. The figures given in the table represent the number of atoms of hydrogen replaced by chlorine per molecule of hydrocarbon.

Table I ggfigg Isa-Octane Compound With Without With Without P205 P205 P205 P105 Uranyl Nitrate 0. l 0. 05 l. 5 0.8 Uranyl Nitrate (dried) 0.25 0.1 2. 6 0.8 Mercurous Nitrate (norma 0.09 0.04 l. 6 0.9 Mercuric Nitrate 0. 06 0. 03 l. 5 l. 7 Zirconium Nitrate (dried)- 0. 2 0. 06 2. 2 0.8 Thorium Nitrate 0.07 0. 03 l. 7 l. 6 Cerium Nitrate 0.3 0.2 2. 4 3. 3 Zine Nitrate (dr1cd) 0. l 0. 2 2. 7 0. 4 Copper Nitrate 0.3 0. l 2. 7 1.4 Cadmium Nitrate (dr1ed) 0.2 0.1 2. 6 0. 4 Calcium Nitrate (dried) 0. 3 0. l 3.0 0. 3 Cobalt Nitrate* 0.0 0.5 Thallium Nitrate 0. 02 0. 3 Lead Nitrate- 0.02 0.1 Barium Nitrate 0.03 0.1 Strontium Nitrate. 0. 03 0. 04 Sodium Nitrate 0. 01 0. l Potassium Nitrate 0.5 '0. 2 1.9 0. 7 Chromium Nitrate 0. 5 0. 1 2. 2 0. 7 None*.. 0.01 0. 02

It is apparent from the table that the nitrates down to and including thallium nitrate were highly selective in their ability to chlorinate'isooctane as compared with their ability to ch10 rinate normal heptane. The remaining nitrates although selective to some degree, were not sufficiently active to have any practical utility for the purpose of this invention. It also a that the selectivity of the catalyst; good $232: 1n the presence or absence of phosphorus pent oxide, but that the activity of the catalyst is greater in the presence of phosphorus pentoxide with the exception of mercuric and cerium nitrates. Another series of tests was made to determine the effect of various nitrates on the chlorination of various saturated hydrocarbons. In this series of tests the reaction conditions of time and tem-' perature were the same as for the tests reported in Table I. The ratio of the reactants was 2 mols of hydrocarbon, one-mol of catalyst, 6 mols of phosphorus pentoxide, 48 mols of antimony pentachloride and 600 mols of chloroform. The fi ures appearing in the table represent the atoms of hydrogen replaced by chlorine per molecule of hydrocarbon, with the exception of th tests marked with an asterisk in which 10 111015 o f'hy droc'arbon, 'one'moi of catalyst, 6 moist: th

. 5 phorus pentoxide, 50 mols of antimony pentachlorideahdi'IlBO mols of chloroform were used carbons cdntaining atertiary carbonatem atap= proximately atmospheric temperature comprising Table-II Uranyl Mercurous Thorium v c n Nitrate Nitrate Nltrt;9;;i

P205 Kg? With 2 "with" gif With Pro-5" P205 P205 P205. Pz Oa P205 P205 n-Pentane 0. a 0. b 0. 05 0 0 o nOctane 0.06 0.08 0.02 0.06 0 0 iso-Pentane 0. 4 1. 5 3. 7 3. 4 3. 5 3. 4 3. 7 4. 0 150 Octane 0. 2 2. 8 2. 6 2.1 Neohexane 01 0(2) 0.? 0.2 g 5 0.2 Eth lc clohe ane 0.06 O. 4 4. Trip ta m f 2. 7 1. 5 8. 5 1.6 4. 1 1. 7 3. 4 1. 6 Cynlnhexanp O 0 Z-Methylpentam 5. 0 4. 7 Methylcyclnheamm 4. 9 4. 8 Demlin 6.3 2,3-Dimethylpentane". 3. 9 2,4-Dimethylpentane". 3. 9

It is apparent from the results in Table II that saturated hydrocarbons not containing a tertiary carbon atom, such as normal pentane, normal octane, neohexane and cyclohexane, show very little, if any, increase in the amount of chlorination in the presence of the various nitrate catalysts. On the other hand, the hydrocarbons having a tertiary carbon atom, such as isopentane, iso-octane and methylcyclohexane, show a marked increase in chlorination in the presence of the catalyst.

In order to demonstrate the selectivity of catalysts in accordance with our invention when used with a mixture of hydrocarbons, three mixtures were prepared and chlorinated with antimony v contacting said hydrocarbons with a chlorinating pentachloride in the presence of phosphorus pentoxide in chloroform solution using uranyl nitrate as catalyst. The amount of isoparafiin in the mixture was determined in accordance with the modified Moldavskii method described in appli cation Serial No. 474,748. The composition of the three mixtures with the isoparafiin content determined by analysis is given in Table 131:

Table III Per cent Per cent Composition of mixture (per cent by Iso-paraifin Iso-paraifin volume) in mixfound by ture analysis Mixture I: 35% n-heptane', 35% iso-octane,

15% di-isobutylene, 15% benzene 35 34. 6 Mixture II: 32.5% n-heptane, 30% isooctane, 15% benzene, 22.5% cyclohexene. 30 33. 8 Mixture III: 32% n-heptanc, 24% isooctane, 20% cyclohexene, 24% benzene 24 29. 2

agent in the presence of a compound selected from the group consisting of nitrosyl chloride and metal nitrates and nitrites, excepting uranium salts, capable of reacting with chlorine under reaction conditions to form nitrosyl chloride.

2. The method of chlorinating saturated hydro carbons having a tertiary carbon atom without chlorinating saturated hydrocarbons not having a tertiary carbon atom in a mixture of said hydrocarbons comprising chlorinating said mixture at a temperature of approximately 70 to 150 F. in the presence of a compound selected from the group consisting of nitrosyl chloride and metal nitrates, excepting uranium salts, and nitrites capable of reacting with chlorine under reaction conditions to form nitrosyl chloride.

3. Method in accordance with claim 2 in which the chlorinating agent is antimony pentachloride.

.4. The method of selectively chlorinating saturated hydrocarbons having a tertiary carbon atom in a mixture containing saturated hydrocarbons not containing a tertiary carbon atom comprising reacting said mixture with antimony pentachloride at temperatures of approximately 70 to 90 F. in the presence of a catalyst selected from the group consisting of nitrosyl chloride and metal nitrates and nitrites, excepting uranium salts, capable of reacting with chlorine under reaction conditions to form nitrosyl chloride the ditions.

6. Method in accordance with claim 4 in which the catalyst is a nitrate of mercury.

7. Method in accordance with claim 4 in which the catalyst is thorium nitrate.

8. Method in accordance with claim 4 in which "the catalyst is cerium nitrate.

9. Method in accordance with claim 4 in which the catalyst is zirconium nitrate.

7 10. Method in accordance with claim 4 in which the reaction'is carried out in the presence of phosphorus pentoxide and the catalyst is zinc nitrate.

GEORGE W. AYERS. ERSKINE E. HARTON, JR.

REFERENCES CITED The following references are of record in the file of this patent:

8; UNITED STATES PATENTS 7 Number Name Date 1,677,831 Krause 'J1'11y 1'7; 1928 2,418,814 Ayers et a1. Apr. 15, 1947 OTHER REFERENCES Eglofi? et aL: Isomerization of Pure Hydrocarbons; pages 407-419 (1942). 

1. THE METHOD OF CHLORINATING SATURATED HYDROCARBONS CONTAINING A TERTIARY CARBON ATOMS AT APPROXIMATELY ATMOSPHERIC TEMPERATURE COMPRISING CONTACTING SAID HYDROCARBONS WITH A CHLORINATING AGENT IN THE PRESENCE OF A COMPOUND SELECTED FROM THE GROUP CONSISTING OF NITROSYL CHLORIDE AND METAL NITRATES AND NITRITES, EXCEPTING URANIUM SALTS, CAPABLE OF REACTING WITH CHLORINE UNDER REACTION CONDITIONS TO FORM NITROSYL CHLORIDE. 